Apparatus and method for cleaning and concentrating fine solids

ABSTRACT

An apparatus and method are provided for the continuous concentration of a fine solids slurry, and are especially adapted for use with fine coal slurries. A tank is provided with upwardly-diminishing dimensions that terminate to form a restricted discharge means for more concentrated slurry. The tank has rotatable drums therein containing suspended stationary magnetic elements, injection means adjacent the tank bottoms for feeding of solids slurry, and ducts positioned below the drums for discharge of less concentrated slurry. Magnetite is fed to the slurry-containing tank which causes separation of coal particles from a fine coal slurry that float to the top of the tank, and with additional slurry being fed to the tank, and by adjusting the volume in the tank with means to regulate flow through the ducts, the desired amount of more concentrated slurry is discharged through the trough while less concentrated slurry is discharged through the ducts. Turbulence is caused by the injected slurry and the magnetic elements in the drums prevent loss of magnetite through the ducts in the bottom, while the shape of the tank and the greater density of the magnetite prevents its escape through the trough at the top, and it is retained and used in the tank.

United States Patent Eugene Cline Lowmansvllle, Ky. 41232 [21] Appl. No.820,347

[22] Filed Apr. 29, 1969 [45] Patented June 8, 197 I [72] Inventor [54]APPARATUS AND METHOD FOR CLEANING AND CONCENTRATING FINE SOLIDS PrimaryExaminerTim R. Miles Assistant Examiner-W. Cuchlinski AttorneyParmelee,Utzler & Welsh ABSTRACT: An apparatus and method are provided for thecontinuous concentration of a fine solids slurry, and are especiallyadapted for use with fine coal slurries. A tank is provided withupwardly-diminishing dimensions that terminate to form a restricteddischarge means for more concentrated slurry. The tank has rotatabledrums therein containing suspended stationary magnetic elements,injection means adjacent the tank bottoms for feeding of solids slurry,and ducts positioned below the drums for discharge of less concentratedslurry. Magnetite is fed to the slurry-containing tank which causesseparation of coal particles from a fine coal slurry that float to thetop of the tank, and with additional slurry being fed to the tank, andby adjusting the volume in the tank with means to regulate flow throughthe ducts, the desired amount of more concentrated slurry is dischargedthrough the trough while less concentrated slurry is discharged throughthe ducts. Turbulence is caused by the injected slurry and the magneticelements in the drums prevent loss of magnetite through the ducts in thebottom, while the shape of the tank and the greater density of themagnetite prevents its escape through the trough at the top, and it isretained and used in the tank.

PATENTED JUN 8 mm SHEET 1 UF 2 INVENTOR. Eugene Clme.

BY fwuJ -L ably W Attorneys.

PATENTEU JUN 8 I911 3583.560

SHEET 2 BF 2 INVENTQR. Eugene Clme.

Attorneys.

APPARATUS AND METHOD FOR CLEANING AND CONCENTRATING FINE SOLIDSBACKGROUND The mechanization of coal mining, both by the use of loadingmachines, and more recently the continuous mining machines, has greatlyincreased the production of fines. As much as fifty percent of theproduction of some of the mining machines which I have sampled passesthrough a /4 inch screen. As a result, equipment and methods heretoforeused to process the fines profitably are no longer adequate for thepresent high rate of production.

One widely used method is the so-called "heavy media process" whereinwater having magnetic particles densely diffused therethrough to form amixture having a higher specific gravity of the coal and a lowerspecific gravity than the refuse is used to float the coal while therefuse sinks. With mixtures other than coal, as for example sand, thesand may sink and the refuse, such as shale, will float. However thefloating material is carried out with the liquid medium and then themagnetic particles must be separated from the water for reuse, usuallyby magnetic separation, and commonly the magnetic particles tended tofloculate, requiring that they be first defloculated for reuse.

SUMMARY The present invention provides a separation vessel havinginwardly-sloping walls leading to a restricted outlet at the top so thatfine solids material of a lesser density such as coal or float materialis forced or crowded by the material of greater density up through theoutlet at the top as a thick concentrate free of most of the flotationliquid. A water slurry of the admixture of fine particles of lesserdensity and fine particles of relatively greater density, such as aslurry of coal fines, to be cleaned is continuously supplied to thelower portion of the vessel under pressure to keep a zone of agitationin a portion of the tank,,and water containing particles of greaterdensity such as sediment refuse is continuously-withdrawn, with theinput and outflow regulated to maintain a substantially constant levelof flotation liquid in the tank below the outlet at the top of thevessel. Means is provided for continuous magnetic removal of themagnetic particles from the outflowing water and discharging themimmediately into the zone of agitation to keep the specific gravity ofthe flotation liquid substantially constant, and under these conditionsno floculation of the magnetic particles occurs. Provision is made foradding makeup particles from time to time as required. In the preferredembodiment, there is a second tank below the first with the outletopenings for the removal of the water and sediment material being in thebottom of the first vessel in closed communication with the second.Rollers are over these outlet openings so that the outflowing liquidflows over their surfaces. Stationary magnets inside the rollers attractthe magnetite in the water to the rollers which then carry the magnetiteout of the magnetic field, and the oxide is released into the turbulentzone created by the incoming slurry.

By the process of continuously crowding the float material free of mostof the water out the top of the vessel and continuously supplying newslurry to the vessel and continuously removing water from the vessel atsuch rate as to maintain a constant liquid level in the tank, and byseparating the magnetic particles from the outflowing water anddischarging them into the incoming slurry, a continuous economical andeffective method of separating and cleaning the coal or other materialis provided.

The objects and novel features of the invention are described in thefollowing detailed description when the same is read in conjunction withthe accompanying. drawings. The drawings are not intended as adefinition of the invention, however, and are for the purpose ofillustration only.

BRIEF DESCRIPTION 'OF THE DRAWINGS FIG. 1 is an exploded perspectiveview of the apparatus of the present invention, with cutaway portions,showing the use of two tanks, one superimposed on the other,

FIG. 2 is a sectional view of the assembled apparatus shown in FIG. 1taken along lines II-II.

DETAILED DESCRIPTION Referring to FIG. I, there is shown the preferredapparatus of the present invention for use in cleaning and concentratingfine coal slurry having a first tank I, and a second tank 41. The firsttank or separating tank 1, has a bottom 3, and upwardlydiminishingdimensions as shown with two end walls 5 and 5' and two upwardly andinwardly extending sidewalls 7 and 7'. The sidewalls 7 and 7 terminatein upwardly and outwardly extending flanges 9 and 9 so as to form arestricted discharge opening or trough 11 at the upper end of thetank 1. Located on the trough 11 are a solids feed means 13, such as afunnelshaped feeder, and a discharge spout 12 for removal ofconcentrated slurry from the apparatus.

The bottom 3 of tank 1 has therein, intermediate the sidewalls 7 and 7and extending between end walls 5 and 5', a channel 15, extendingdownwardly. Positioned in the channel 15 is an injection means 17,herein illustrated as a pipe 19, with apertures 21 therein for injectinga fine coal slurry upwardly in the tank 1.

Positioned between the channel 15 and the sidewalls 7 and 7 are a pairof rotatable drums 23 and 23', one of the drums 23 and 23 located oneach side of the channel 15 and being rotatable in an upward and inwarddirection in the tank 1 to direct a current of liquid towards the centerof tank 1 and upwardly towards the flow of slurry from channel 15. Ineach of the drums 23 and 23' there are suspended, in a stationaryposition, magnetic elements 25 and 25'. The magnetic elements arestationary and extend downwardly so that even as drums 23 and 23'rotate, a magnetic force is always exerted towards the bottom 3 oftank 1. Preferably, the magnetic elements 25 and 25 are suspended by astationary rod, such as 27 and 27' illustrated in the drawings. Thedrums 23 and 23 may be made rotatable by positioning them aroundstationary shafts or rods 27 and 27' which support a suitable sleeve andcoupling means at the tank ends, the sleeve being journaled for rotationby suitable drive means 16 powered by a motor 28. The means for rotatingthe drums 23 and 23' in opposed directions would be readily discernableto one of mechanical skill, such as by a belt 30, idler 32 and suitablewheel members 34, or a chain and sprocket-type device.

Below the drums 23 and 23 and positioned in the bottom 3 of tank 1 are apair of ducts 31 and 31'. These ducts 31 and 31' permit exit from thetank 1 of the less concentrated coal slurry according to the method asmore fully described hereinafter. Preferably, these ducts are positionedin concavities in the bottom 3 so as to conform the bottom to the drumshapes.

In the preferred embodiment of the apparatus of the present invention,there is located, beneath the first tank 1, a second tank 41, both tanksbeing interconnected, in closed communication, by means of the ducts 31and 31'. The second tank 41 preferrably has generally sloping sidewalls43 and 43' and end walls 45 and 45', which extend downwardly andinwardly to form a bottom 46 having thereon drainage means 47, hereinillustrated as an orifice 48 and, as described hereinafter, a pump 57,to provide for ready regulation of the volume of material in the firsttank 1, and also regulate outflow from the total apparatus.

Also illustrated in FIG. 1 are the various feed means and controls forfeeding fine coal slurry to the apparatus and removing more concentratedand less concentrated slurries therefrom. Illustrated therein are line51 having valve means 35 therein. Line 51 is attached to feed pipe 19and to connecting line 54. Connecting line 54 interconnects line 51 andthe second tank 41 at pump 57 and has valve 36 thereon. For

discharge of less concentrated slurry or clear water there is provideddischarge means on tank 41, herein illustrated as line 59 and adjustablevalve 61 to control flow therefrom.

The method for concentrating a fine coal slurry using the apparatus ofthe present invention is as follows. With valves 36 and 61 in closedposition, valve 35 is opened and a fine coal slurry fed therethrough.The fine coal slurry is fed with sufficient pressure by means of a pumpor strong gravity feed or other means (not shown) so as to force finecoal slurry into feedpipe 19 and inject the slurry through apertures 21upwardly into first tank 1. As the fine coal slurry falls, by gravity,to the bottom 3 of tank 1, the slurry will flow through ducts 31 and 31and into second tank 41. Continued flow will fill tank 41, ducts 31 and31' and eventually cause a buildup of fine coal slurry in tank 1. Whentank 1 is filled to a predetermined volume, the power source isactivated and drums 23 and 23' caused to rotate in the direction asindicated in FIG. 2. With drums 23 and 23' rotating, a predeterminedamount of magnetite (m) is fed to tank 1, through solids feed means 13,(not shown on FIG. 2). Adjustable valve 61 is then opened and set so asto allow the continuous discharge of a predetermined amount of liquid,the amount being determined based upon the percent of solids in the finecoal slurry entering tank 1 through injection means 17.

As the fine coal slurry (s) is fed to the tank 1 by injection means 17,the fine coal particles suspended in the slurry will, because ofdensity, float to the top portion of tank 1 and form a layer on theslurry. The depth of the layer of more concentrated slurry (S) or coalparticle phase is adjustable by varying the amount of slurry in tank 1,through manipulation of adjustable valve 61 and regulating the flow ofless concentrated slurry (s') which flows through ducts 31 and 31' intosecond tank 41. The depth of the coal particle phase or moreconcentrated slurry is adjusted so as to prevent loss of magnetite whichhas been fed to the tank 1 through overflow into trough 11. Thus, incontinuous operation, more concentrated slurry is permitted to flow fromthe tank 1 by means of trough 11, and less concentrated slurry isexhausted from tank 41 by means of line 59 and adjustable valve 61, themagnetite is maintained and continuously reused.

As seen in FIG. 2, wherein magnetite (m has been added to the slurry butthe level of the total aqueous suspension is below that for removal ofmore concentrated slurry (S), the fine coal slurry is fed into the tank1 through apertures 21 in pipe 19 in the form of jet streams whichagitate the slurry contained in tank 1. The streams weaken as they reachthe upper region of the tank and can be adjusted by means of thepressure source to provide the desired turbulence. The jet streamsprevent settling of magnetite in channel of the bottom 3 of tank 1 whilethe fine coal particles float to the top portion of tank 1. Thisturbulence and the various densities of the materials cause the lessconcentrated slurry, with magnetite, to flow towards the sidewalls 7 and7 of tank 1 and thence downwardly to the region of ducts 31 and 31'below drums 23 and 23'. With the stationary magnetic elements 25 and 25'positioned adjacent ducts 31 and 31', the magnetite is attracted to thesurfaces 26 and 26' of the drums 23 and 23' while the less concentratedslurry flows by gravity through the ducts 31 and 31 and eventually isdischarged by means of line 59 and adjustable valve 61.

The magnetite attracted to drums 23 and 23' is held to the surfaces 26and 26 thereof until it is sufficiently removed from the magnetic forcesof magnetic elements 25 and 25' and is released from the drum surfaceand urged upwardly towards the center portion of the tank above channel15. Magnetite particles, often flocculated by the magnetic influence,are urged into the region'of channel 15 and are broken up into finerparticles by the influence of the jet streams exiting from injectionmeans 17 The fine coal slurry is thus fed to the apparatus and becauseof the magnetite present, more concentrated slurry is provided in theupper region of the tank 1, with discharge thereof through trough 11,while less concentrated slurry is directed to the bottom 3 of tank 1,and through ducts 31 and 31'. The magnetite is maintained in tank 1, bythe magnetic field exerted by magnetic elements 25 and 25', and directedtowards the turbulence caused by injection of additional fine coalslurry to maintain the magnetite in dispersed form suitable for furtherconcentration of fine coal slurry.

Should it be desired to remove the magnetite from the apparatus,suitable means can be provided to permit the adjust ment of the magneticelements 25 and 25 to an upward position. Any magnetite in the region ofthe surfaces 26 and 26 of bottom of drums 23 and 23' will thus besufficiently removed from the magnetic field and will fall by gravitythrough ducts 31 and 31 into tank 41 where it can be removed therefromby actuating pump 57 to discharge the contents of tank 41. The magnetiteso removed may be returned to tank 1 by means of pump 57, connectingline 54, through opened valve 36 and, with valve 35 closed, into feedline 19. Other means of breaking the magnetic field, such as insertionof a suitable shield between the magnets 25 and 25' and the drum surface26 and 26' are, of course, also usable.

As an example of a suitable apparatus and process, the tank 1, can varybetween two 5: feet to ten feet in length. The tank 1, being of generaltriangular configuration along a cross section thereof, allowsmaintenance of a greater height between the top surface of theconcentrated slurry and the remaining magnetite suspension, allowingdischarge of the more concentrated slurry without any great danger ofloss of magnetite suspension therewith. Proportionately, the second tank41, should have a capacity to hold all of the magnetite from tank 1 fordrainage purposes. As an example of the concentration of the fine coalslurry according to the present process, a feed of fine coal slurrycontaining about 10 percent solids may be fed to the desired volume intank 1 and adjustable valve 61 adjusted to discharge percent of thetotal volume of the subsequent feed, with 20 percent of the total feeddischarged through the trough 11 of tank 1. Such a more concentratedslurry would thus contain about 50 percent solids or fine coalparticles.

Although the invention'has been described with specific emphasis onconcentration of fine coal slurries, the invention is adaptable forother separations where fine particles of lesser density are to beseparated from an admixture with fine particles of a greater density. Anexample of such would be the separation of shale or other materials oflesser density from sand, a material or greater density. in such aseparation, the sand or heavier material would be the desirable cleanedproduct and would be subsequently removed from the outflowing waterwhile the shale or other lighter material would be removed as theconcentrated slurry from the top of the vessel and discarded.

There have been provided, according to this invention, an apparatus andmethod especially useful for concentrating a fine coal slurry where theless concentrated portion of the slurry is substantially free of solidparticles. The more concentrated slurry contains a high solids contentso that conventional equipment can readily complete the separation ofthe fine coal from the more concentrated slurry at a much greatercapacity. The apparatus and process do not involve subsequent separationof magnetite from either the more or less concentrated slurries and themagnetite is maintained and reused continuously.

lclaim:

1. An apparatus for separating fine solid materials of a lesser densityfrom admixture with fine solid materials of a greater density byflotation in a mixture of water and magnetic particles comprising a. avessel of upwardly-diminishing dimensions having means at the upperregion thereoffor discharge of lesser density solids,

b. means for charging magnetic particles into said vessel,

c. means in the lower region of the vessel for continuously injectingsaid admixture of solid particles with water upwardly into said vessel,

d. an outlet in the lower portion of said vessel for the continuousdischarge of water containing said solid materials of a greater density,and

e. means in the path of the outflowing water to remove magneticparticles therefrom and discharge them into contact with said upwardlyinjected admixture.

2. The apparatus of claim 1 wherein said means in the path of theoutflowing water to remove magnetic particles therefrom comprises atleast one rotatable drum suspended in said vessel having thereinstationary magnetic elements so positioned as to exert a magnetic fieldtowards the bottom of said vessel.

3. Apparatus for concentration of coal fines by flotation in a mixtureof water and magnetic particles comprising:

a. a vessel of upwardly-diminishing dimension terminating at the top ina restricted discharge opening for concentrated coal slurry,

b. means in the bottom of the vessel for continuously injecting a slurryof raw coal fines into the vessel to agitate the contents of the vessel,

c. means for introducing magnetic particles into the vessel,

d. an outlet means for the continuous discharge of water having sedimentmaterial and some coal fines from the lower portion of the vessel, and

e. means in the path of the outflowing water arranged to remove magneticparticles therefrom and discharge them adjacent the incoming slurry ofraw coal fines.

4. The apparatus of claim 3 wherein said vessel has a bottom, two endwalls and two upwardly and inwardly extending sidewalls, said means forcontinuously injecting said slurry is positioned in a channelintermediate the sidewalls of the vessel, said outlet means comprises apair of ducts in the bottom of said vessel, and said means arrangedtoremove magnetic particles from the outflowing water comprises a pairof rotatable drums suspended in the vessel and having a magnetic elementsuspended therein in a generally downwardly extended stationaryposition.

5. The apparatus of claim 4 wherein said ducts are positioned inconcavities formed in said bottom which generally conform to saidrotatable drums.

6. The apparatus of claim 4 wherein said injection means comprises agenerally horizontal pipe extending between said end walls and having aplurality of apertures in the upper portion thereof through whichpressurized fine coal slurry is dispersed.

7. The apparatus of claim 4 wherein each of said magnetic elements issuspended so as to exert a magnetic force in the area between said ductand said channel.

8. The method of continuously separating fine particles of a lowerdensity from fine particles of a higher density admixed therewith byflotation in a medium of water having magnetic particles diffusedtherethrough to provide a heavy medium comprising the steps of:

a. confining the heavy medium in an enclosed vessel ofupwardly-diminishing dimension with an overflow outlet at the top,

b. continuously introducing a slurry of said admixture to be processedinto said confined heavy medium and maintaining a zone of agitationtherein,

c. continuously discharging a concentrated slurry of fine particles oflesser density upwardly through the overflow outlet,

d. continuously withdrawing high density particles and water from whichfine particles of lesser density have been removed from the vessel whileseparating the magnetic particles from the high density particles andwater and immediately discharging the magnetic particles into the zoneof agitation, and

e. regulating the inflow of slurry and the removal of concentratedslurry and the removal of water to maintain a substantially constantlevel of flotation liquid in the vessel below said overflow outlet. 9.The method of claim 8 wherein said slurry comprises coal fines andrefuse in aqueous admixture and concentrated slurry of clean coal finesis removed through the overflow outlet.

10. ln a method for concentrating a fine coal slurry and removingimpurities therefrom wherein an aqueous magnetite suspension is presentwhich raises the specific gravity of the slurry to cause the fine coalparticles to float to the top of said suspension while impurities settleto the bottom of the suspension, the improvement comprising,

a. injecting said fine coal slurry in the form of upwardly directedstreams into said suspension whereby fine coal particles float to form amore concentrated slurry at the upper region of said suspension whileimpurities, magnetite and resultant less concentrated slurry settle tothe lower region of said suspension,

b. subjecting said settling magnetite particles to a magnetic fielddirected from a rotating drum, which field causes said magnetiteparticles to be drawn to and held by the surface of said rotating drum,while said impurities and resultant less concentrated slurry areuneffected by said field,

. removing the magnetite particles from said magnetic field throughrotation of said drum, whereby said magnetite is discharged from saiddrum surface and directed into said upwardly directed streams forfurther concentration of additional fine coal slurry comprising saidstreams,

(1. while removing a predetermined amount of said less concentratedslurry from said lower region and a concomitant predetermined amount ofsaid more concentrated slurry from the upper region of said aqueousmagnetite suspension.

2. The apparatus of claim 1 wherein said means in the path of the outflowing water to remove magnetic particles therefrom comprises at least one rotatable drum suspended in said vessel having therein stationary magnetic elements so positioned as to exert a magnetic field towards the bottom of said vessel.
 3. Apparatus for concentration of coal fines by flotation in a mixture of water and magnetic particles comprising: a. a vessel of upwardly-diminishing dimension terminating at the top in a restricted discharge opening for concentrated coal slurry, b. means in the bottom of the vessel for continuously injecting a slurry of raw coal fines into the vessel to agitate the contents of the vessel, c. means for introducing magnetic particles into the vessel, d. an outlet means for the continuous discharge of water having sediment material and some coal fines from the lower portion of the vessel, and e. means in the path of the outflowing water arranged to remove magnetic particles therefrom and discharge them adjacent the incoming slurry of raw coal fines.
 4. The apparatus of claim 3 wherein said vessel has a bottom, two end walls and two upwardly and inwardly extending sidewalls, said means for continuously injecting said slurry is positioned in a channel intermediate the sidewalls of the vessel, said outlet means comprises a pair of ducts iN the bottom of said vessel, and said means arranged to remove magnetic particles from the outflowing water comprises a pair of rotatable drums suspended in the vessel and having a magnetic element suspended therein in a generally downwardly extended stationary position.
 5. The apparatus of claim 4 wherein said ducts are positioned in concavities formed in said bottom which generally conform to said rotatable drums.
 6. The apparatus of claim 4 wherein said injection means comprises a generally horizontal pipe extending between said end walls and having a plurality of apertures in the upper portion thereof through which pressurized fine coal slurry is dispersed.
 7. The apparatus of claim 4 wherein each of said magnetic elements is suspended so as to exert a magnetic force in the area between said duct and said channel.
 8. The method of continuously separating fine particles of a lower density from fine particles of a higher density admixed therewith by flotation in a medium of water having magnetic particles diffused therethrough to provide a heavy medium comprising the steps of: a. confining the heavy medium in an enclosed vessel of upwardly-diminishing dimension with an overflow outlet at the top, b. continuously introducing a slurry of said admixture to be processed into said confined heavy medium and maintaining a zone of agitation therein, c. continuously discharging a concentrated slurry of fine particles of lesser density upwardly through the overflow outlet, d. continuously withdrawing high density particles and water from which fine particles of lesser density have been removed from the vessel while separating the magnetic particles from the high density particles and water and immediately discharging the magnetic particles into the zone of agitation, and e. regulating the inflow of slurry and the removal of concentrated slurry and the removal of water to maintain a substantially constant level of flotation liquid in the vessel below said overflow outlet.
 9. The method of claim 8 wherein said slurry comprises coal fines and refuse in aqueous admixture and concentrated slurry of clean coal fines is removed through the overflow outlet.
 10. In a method for concentrating a fine coal slurry and removing impurities therefrom wherein an aqueous magnetite suspension is present which raises the specific gravity of the slurry to cause the fine coal particles to float to the top of said suspension while impurities settle to the bottom of the suspension, the improvement comprising, a. injecting said fine coal slurry in the form of upwardly directed streams into said suspension whereby fine coal particles float to form a more concentrated slurry at the upper region of said suspension while impurities, magnetite and resultant less concentrated slurry settle to the lower region of said suspension, b. subjecting said settling magnetite particles to a magnetic field directed from a rotating drum, which field causes said magnetite particles to be drawn to and held by the surface of said rotating drum, while said impurities and resultant less concentrated slurry are uneffected by said field, c. removing the magnetite particles from said magnetic field through rotation of said drum, whereby said magnetite is discharged from said drum surface and directed into said upwardly directed streams for further concentration of additional fine coal slurry comprising said streams, d. while removing a predetermined amount of said less concentrated slurry from said lower region and a concomitant predetermined amount of said more concentrated slurry from the upper region of said aqueous magnetite suspension. 